Rapid Prototyping

Com270-011
Professor Gail Rosen
March 7, 2002

Rapid Prototyping

Every company that produces a product, whether it be an industrial water pump, or a ladies' satin pump, has a research and development team. The main task of these teams is to come up with the design for a product, make it feasible, and come up with prototypes to be reviewed by members of the R&D team as well as other members of the company.

As one could imagine, the research and development team play a very important role in a company. The ability to come up with a new product quickly is what makes the difference between a market leader and a follower. In many cases, this is the difference between success and failure. Because of this, most companies seek to shorten their research and development time.

As was stated earlier, however, the research and development process is very important, and therefore should not be rushed. It is very difficult, and in many instances impossible, to produce an article that will serve the purpose of use without making at least some minor modifications to the original shape or general design. There are many examples of design failure that have been the cause of serious injury and costly litigation. The only way to improve upon the process is to make it more efficient, through the use of improved techniques and improved technologies.

Nowadays, the process of research and development for most products includes the use of a vast array of computerized systems and programs. The initial concept of a product begins as an image in a design manager's mind. Through whatever means possible, he translates this concept to those on the research and development team. More often than not, it is little more than a few lines sketched onto a piece of paper.

This image is then translated to 3D form via the use of a 3D modeling program. Some companies use their own proprietary programs, but many use commercially available programs such as 3D Studio Max or SoftImage. In the program, a designer is able to create and manipulate a 3D model of the concept. This 3D model is saved as a file, and is therefore a semi-permanent blueprint of the product's design. This concept is then made into a tangible object called a prototype.

Conventionally, this stage is very time consuming. A single prototype can take months to build. A scale model of the concept is built, and is reviewed by the design manager. The design manager can then take a look at what the product will really look like and make decisions about what should be changed or adjusted. Revisions are made to the prototype, which may take another month or two, and then the design manager will review it again. This cycle can (and usually does) repeat itself numerous times. Once the prototype is approved, it will go down the line to production and manufacturing to be made into the final product.

Obviously, the model building or prototyping stage consumes a large amount of time. The laborious task of creating and revising a scale model can only be done by those working closely with the concept at hand. Luckily, a new model building technique has come to pass. The method is called 'rapid prototyping', and it can drastically reduce scale model build times.

Rapid prototyping is a process by which a 3D model is translated into a tangible object, by way of a mechanical device. This mechanical device is called a 3D printer and has been derived from stereo lithography. The stereo lithography process is more involved and more time consuming than the current 3D printing technique. The stereo lithography system consists of an Ultra-Violet Laser, a vat of photo-curable liquid resin, and a controlling system.

A mechanically controlled elevator system lowers a platform into the resin in a way that the surface of the platform is a layer-thickness below the surface of the resin. A laser beam is then guided along the perimeter of the object to be constructed, and fills in a two-dimensional cross section of the model. The laser solidifies the resin wherever it touches. Once a layer is complete, the platform descends a layer thickness, resin flows over the first layer, and the next layer is built. This process continues until the model is complete.

Once the model is complete, the platform rises out of the vat and the excess resin is drained. The model is then removed from the platform, rinsed of excess resin, and then placed in a UV oven for a final curing. Even after all of that, you still have to sand it down to remove "stair-steps", which are artifacts formed by the technique itself.

It is obvious that this technique would need to be improved upon before being used for rapid prototyping. The 3D printer is just such an improvement. It operates under the same fundamental principles, but does so in a much more tidy fashion. The device uses a powder instead of a liquid, and uses a binding agent instead of a laser. These differences allow the equipment to use up much less space, as well as reduce the cost of equipment and maintenance.

The powder is applied to a surface, the binder rolls over the powder, applying the binding agent to specific areas, creating a layer of the object. Once the model is finished, the excess powder is vacuumed away and can be reused. The layering process is more precise than that of stereo lithography, and therefore, sanding is not necessary after the printer has finished. In addition to this improvement on the process, you can also have the printer output in multiple colors. This provides for a more realistic model, and illuminates the need of post-build painting.

Many companies in the US are already realizing the benefits of the 3D printer. "We wanted to get physical models more quickly… ones that looked more like what the real parts would look like," says Eric Bartkus, a project engineer at Access. According to Access, a unit of the Alticor family of companies, "brewing good coffee requires careful engineering". Among other things, Access produces coffee makers, and they use rapid prototyping to do so. Bartkus says that they migrated to rapid prototyping in an effort to achieve dimensional accuracy and reduce the time required to create models. One advantage of the system is its ability to build parts unattended, enabling it to run around the clock

Recently, Access used the system to model a coffee carafe for one of its products, the KAHVE coffee maker. It was a runner-up in the 13th annual Excellence in Design competition. A goal of the project was to design a stylish handle that offered a good fit and feel for all hand sizes. Access also created a model of the coffee maker itself to use in a rapid tooling process. The tool was poured around the model to form the cavity and the core. From the mold, Access built a short run of 100 units for testing.

Access engineer Steve Mork estimates that using the rapid prototyping system shaved 15 days off the schedule. "At an average program cost of $1,000 a day, that adds up quickly," Mork says. Over the course of 19 months, Access built nearly 450 models. Building them with rapid prototyping saved them almost a quarter of a million dollars.

Chrysler engineers use rapid prototyping as part of the overall design process. They have found that the printed models serve another purpose separate from prototyping. It is now being used as a way to communicate with customers and original equipment manufacturers about upcoming products. They also use it for wind tunnel testing.

Chrysler, as well as most of its competitors, has been using scale models for decades. Designers began using them as a visual review tool. In the middle 1960's, Chrysler's aerodynamicists began using hand-built models for wind tunnel testing.

One mock-up department member might build 3/8-scale models of vehicle underbodies and engines. The underbody and engine models are then assembled with the outer body surface of the vehicle, which is usually made of clay, for wind tunnel testing of the complete 3/8-scale vehicle model. Then the 3-D printed models of the parts are incorporated into the scale vehicle that will go into the wind tunnel. The 3D printer is credited with cutting as much as 90 percent from the typical 13 to 15 weeks previously needed to hand-build models for wind tunnel testing.

Chrysler has found that a 3-D printer, once purchased, can be used for a variety of purposes, including showing prototyped parts to customers and tweaking prototyped parts in real life and, in some cases, sometimes using them as a mold to make parts.

This new spin on an old method is certainly a step in the right direction. The incorporation of a 3D printer into the prototyping process is an example of sound judgment. Both Access and Chrysler have seen tremendous results through the use of rapid prototyping. The technique saves time and money, and in many cases, can wield results that are better than those possible without it. It is conclusive that rapid prototyping and 3D printers will be useful tools in the future of design and research and development.

Bibliography

Jones, Charmaine. "Rapid Prototyping = Rapid Time to Market." 27 Sept. 2001
<http://www.ammagazine.com>.

"3D modelling a big success for scanner designers." 24 January 2002
<http://www.engineeringtalk.com/news/cdc/cdc104.html>.

"Printing in Three Dimensions." The American Society of Mechanical Engineers 2001
<http://www.memagazine.org>.

"3D Systems." World Business Review
<http://www.wbrtv.com/underwriters/3d_systems>.